Remediation of Acidic Drainage Waters Using Chemical and Natural Materials: Neutralization and Removal of Potentially Toxic Trace Elements (As, Be, Tl, Fe)
Acidic sulfate-rich drainage waters generated during the storage of cyanidation tailings near Ursk (Kemerovo region, Russia) contain trace elements at concentrations far exceeding permissible limits. The objective of this study was to evaluate the effectiveness of chemical and natural materialslimedolomite flour, sodium sulfide (NaS), wood ash, and granulated chicken manurefor neutralizing acidity and removing potentially toxic levels of dissolved elements. Field experiments involved sequential reagent addition with monitoring of pH, redox potential, and elemental concentrations. The chemical transformations were further interpreted using physicochemical modelling to predict the stability of dissolved and precipitated species. Among the tested materials, NaS demonstrated the highest efficiency, precipitating up to 24 mg of metals per gram of reagent and removing more than 92% of As, Be, and Tl. With increasing pH (79), metals transformed from mobile dissolved ions and sulfate complexes into less hazardous hydroxide and carbonate species. Neutralization reactions were accompanied by precipitation of gypsum, hydrous copper sulfates, konyaite, and related hydrous sulfates. Water quality was assessed using the heavy metal pollution index (HPI), which decreased to values well below the critical threshold of 100 after treatment. The lowest index was obtained for NaS-treated waters (HPI = 16.1), confirming its superior performance. This study demonstrates that both chemical and natural reagents can improve the quality of acidic drainage waters, with NaS providing the most effective remediation. The findings highlight the importance of physicochemical modelling in predicting contaminant behaviour during neutralization processes.
